Motor-control system



Oct. 9, 1928. 1.686,948

E. M. BOUTON MOTOR CONTROL SYSTEM Filed July 27, 1922 F 7.1 1 W6 1 g3 24 Pole BPoie p I g L E WITNESSES: [d INVEYNTOR GPA 1.50am

(1 ATTORNEY Patented Oct. 9, 1928.

EDGAR M. BOUTON, OF EAST PITTSBURGH,

TENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIG & MANUFACTURING COMPANY, A' CORPORATION OF PENNSYL- VAN IA.

Application fi led July 27,

My invention relates to systems of control and it has'particular relation to systems that are adapted for the control of two-speed alternating-current motors for elevators,

6 hoists and the like.

One object of my invention is to provide a system of speed control for an alternating. current motor which shall be simple and efiicient in operation. 1

Other objects of my invention will be evident from .the following specification and the appended claims. p

I propose to employ an alternating current motor in connection with my control system, 15 having two speeds corresponding to windings of different numbers of poles, and preferab y of the slip-rin or wound-rotor type. The secondary win ings are suitably connectedto five slip rings, to which are also connected 20 two sets of auxiliary resistors. The resistors are star-connected and have sections thereof common to the circuits of both the high and the low-speed motor windings. Separate accelerating switches are employed for controlling the resistors, but a single accelerating relay is utilized for controlling the accelera- .tion and deceleration of the motor.

My invention will be more clearly understood by reference to the accompanying drawing, in which the single figure is a diagrammatic representation of circuits and apparatus embodying my invention.

In the drawing, a single motor is shown as provided with a low-speed primary winding -1, a low-speed secondary winding 2, a highspeed primary winding 3 and a high-speed secondary winding 4, all of the windings being illustrated'as star-connected. The primary windings are respectively connected through pole-changing switches 5 and 6 to supply conductors 7, 8 and 9. For reversing, service, of course, the supply conductors are to be connected to the line conductors through reversing switches of any well-known type. For simplicity, I have not shown such reversingmeans.

The motor secondary windings may have unlike characteristics, that is, di'fierent normal values of voltage and current during operation. The 10 -speed secondary winding 2 is connected in star relation to accelerating resistors 11, 12 and 13. The high-speed secondary winding 4 is connected in star relationto the secondary resistors 14, 15 and 16.

MOTOR-CONTROL SYSTEM.

1922. Serial No. 577,828.

It will be noted that the resistor section 13 is common to the circuits of both the high and the low-speed windings.

I employ a single accelerating switch 17 for the low-speed windings 2 and a, plurality of accelerating switches 18, 19 and 20 for the high-speed Winding 4. The several accelerating switches are controlled by means of amultiple-finger current-limit relay 21. This A coil 22 of the relay 21 is connected through switch 6 to conductors 7 and 9. A calibrating conductors 7, 8 and 9.

coil 23, also constituting a part of the relay 21, is connected through a control resistor 24' across the resistor-sections 13 and 16. Co l 23 is, therefore, energized in accordance with the current traversing the resistor sections 13 and 16 to prevent the immediate closure ofthe relay contact members 25, 26 and 27 which are arranged to successively engage contact members 28, 29 and 30, respectively, in a manner fully disclosed in the abovementioned patent.

When coil 22' is energized; it releases contact members 25, 26 and 27 which are then restrained only by the action of the calibrating coil 23. As the motor accelerates, varia- I tions occur in the potentialaeross the resis-- tor sections 13 and 16, permitting the release of contact membersi25, 26 and 27, which suc-,

cessively engage contact members 28, 29 and 30.to complete circuits for the operating coils of accelerating switches 18, 19 and 20, The acceleration of the motor is thus, controlled in a well-known manner in accordance with the drop in potential across the acceleratin resistors 13 and 16, as fully disclosed in tfie. above-mentioned patent.

When the motor has attained full speed and it is thereafter desired to reduce the speed, this result may be accomplished b' opening the switch 6 and-closm g the 5, which action motor windings low-speed windings ing relay 21 is promptly reset upon interruptor sections 11, 12

tion of the circuit of coil 22, in turn causing the reinsertion of the accelerating reslstors in the hi gh-speed secondary circuit.

The closure of switch 5 energizes the low-' speed windings 1 and 2; and the motor, which has been running at a speed considerably in excess of the synchronous speed cor responding to the low-speed wind1ngs, 1s now subjected to a dynamic-braking action, as will be understood.

During the initial braking period, the resisthe secondary winding 2, being chosen of suitable ohmic value to limit the current and counter-torque of the motor, until the motor speed has been materially reduced, after which the resistor sections 11,12 and 13 are excluded from circuit by the action of the relay 21, the calibrating coil 23 being subject to the voltage-drop across the resistor section 13. The resistor section 16 is not included in the operating circuit of the low-speed motor winding 2 and this resistor section, therefore, carries only a low value of current, which is the value of current traversing the coil 23.

During the period of deceleration, the relay contact members 25, 26 and 27 are controlled in accordance with the drop in potential across the resistor section 13. The oper-. ating coil of switch 17 should be connected to whichever one of these contact. members provides the most suitable time interval for cutting out the low-speed secondary resistors, it being here shown as connectedto the middle contact member 26 for excluding resistor sections 11, 12 and 13from'the motor circuit.

The motor now operaates substantially at its lower synchronous speed, the speed varying, of course, 1n accordance with load conditions.

In elevator service, it will be understood that, at times, the motor is required to elevate heavy loads and that, at other times, the motor is driven or overhauled by the load. It is especially necessary, under these load conditions, to prevent a too sudden change in the operating speed of the motor, for which purpose I employ the resistor sections and the current-limit relay, in the manner described.

By the illustrated interconnection of the main secondarywindings and resistors, I am able to employ a single relay for controlling both the acceleration and deceleration of the motor, thereby greatly lessening the amount of control apparatus that is required to accomplish the desired results. It is manifest that, when desired, the motor may be started by the low-speed winding prior to its operation at high speed. I have described. the usual method-of starting, that is, by the highspeed windings, as I desire more particularly and 1 3 are in circuit with 1. The combination with an alternatingcurrent motor having windings correspond ing to different speeds and separate accelerating switches for each'speed winding, ofa single accelerating relay for controlling said switches.

2. The combination with an alternatingcurrent motor having a low and a high-speed winding and separate accelerating switches for each speed winding, of an accelerating relay having a single calibrating coil for rendering said switches effective to gradually accelerate the motor.

3. The combination with an alternatingcurrent motor having separate low and highspeed windings, of an accelerating resistor, means for connecting a portion of said resistor in circuit with either winding and another portion of the resistor in circuit with only one of said windings, and an accelerating coil in shunt relation to said resistor.

4. The combination with an alternatingcurrent motor having low and high-speed windings and a resistor connected to a junction-point thereof, ,a portion only of said resistor being energized by the low speed winding, of an accelerating relay having a coil responsive to the drop in potential across the entire resistor for controlling the operation of the motor with eitherspeedwindingin circuit.

5. The combination with an alternatingcurrent motor having low and high-speed windings and a resistor connected to a junction-point thereof, of an accelerating relay responsive to predetermined changes in the voltage across the resistor for controlling the effect of said speed windings, said relay controlling separate high and low-speed contact members.

6. In combination with an alternatingcurrent motor having high and low-speed windings. circuits for said windings including predetermined values of resistance, means for varying the resistance of said circuit for controlling the rate of change of speed of said motor between zero speed and substantially synchronous speed of said highspeed winding comprising a relay having a coil connected in both the highand low-speed windings for energization by voltage in said windings, asecond coil connected for constant voltage opposing the effect of said first named coil, and meansoperable by variations in the combined eflects of said coils for varying the resistance of said circuits, as said motor speed increases and decreases with either of said windingsin use.

In testimony whereof, I have hereunto subscribed my name this 15th day of July, 1922.

anean M. BOUTON.

is present in the 

